Model SS-3M: Medium DutyModel SS-3H: Heavy Duty
Every antenna system should have a spring. Springs proterct your antenna,
your mount, and your vehicle. Firestik springs are made from top grade
stainless steel and chrome-plated machine brass end pieces. They are made
to last. The medium duty is for antennas up to 36" , and the heavy duty
is for antennas up to 60". Fits all Firestik antennas, mount and
accessories.